Flat panel lighting device and driving circuitry

ABSTRACT

The light fixture includes a frame configured to define a channel, and a substantially flat light emitting diode (LED) panel disposed within the frame. Power circuitry is disposed within the first channel, the power circuitry being configured to electrically couple the substantially flat LED panel to an external AC power supply. The power circuitry is sized to be positioned within the first channel and has a length and a width, the length-to-width ratio being at least 5 to 1, and optionally at least 10 to 1. The power circuitry is configured to convert an AC input into a DC output suitable for powering the substantially flat light emitting diode (LED) panel. The substantially flat light emitting diode (LED) panel includes an optically transmissive panel, and an array of LEDs disposed adjacent to an edge of the optically transmissive panel and disposed adjacent at least one edge of the frame.

RELATED APPLICATION DATA

This application is a continuation of U.S. Ser. No. 14/497,943, entitled“FLAT PANEL LIGHTING DEVICE AND DRIVING CIRCUITRY”, filed Sep. 26, 2014,which is a continuation of U.S. Ser. No. 13/473,929, entitled “FLATPANEL LIGHTING DEVICE AND DRIVING CIRCUITRY”, filed May 17, 2012. Thepresent application claims benefit of U.S. Provisional App. No.61/487,253, filed May 17, 2011, which is incorporated by reference inits entirety. The present application also claims benefit of U.S.Provisional App. No. 61/579,472, filed Dec. 22, 2011, which isincorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates generally to lighting assemblies, and moreparticularly to a versatile, substantially flat panel light emittingdiode lighting assembly and associated driving circuitry.

BACKGROUND

For years, lighting systems, such as ceiling mounted lighting fixturesor luminaires, have made use of fluorescent lamps and/or incandescentlamps. In addition to the lamps, lighting systems typically include anassembly of components, such as ballasts and reflectors. Luminaires thatincorporate fluorescent lamps are the most commonly used commerciallight sources due to their relatively high efficiency, diffuse lightdistribution characteristics, and long operating life. Luminaires thatincorporate light emitting diodes are emerging as an attractivealternative to fluorescent lamp luminaires, providing markedimprovements in efficiency and operating life.

Over the lifetime of a lighting system, for example, a commerciallighting system, the expenditures associated with operating andmaintaining the system can be significant. As lighting fixtures age anddeteriorate, the light-emitting ability degrades and the light outputper unit of consumed electrical energy is significantly reduced. Modernballasts, lamps and reflectors are available that can significantlyenhance the light-emitting ability of the lighting system and alsosignificantly enhance the energy efficiency by reducing the powerconsumption. As a result, the light output could be increased, whilesimultaneously reducing the associated energy costs. In manyapplications, long operating life, which reduces the burden ofmaintaining or replacing light fixtures, is seen as an importantcharacteristic.

SUMMARY OF INVENTION

One aspect of the disclosed technology relates to a light fixtureincluding a frame having a thickness of no more than about 1.0 inchesand including a first portion of the frame and a second portion of theframe, wherein the first portion of the frame defines a first channelbetween a first edge of an optically transmissive panel and a firstouter edge of the frame; a substantially flat light emitting diode (LED)panel disposed within the frame, wherein the substantially flat LEDpanel includes an LED strip and the optically transmissive panel, andthe optically transmissive panel is configured to distribute lightreceived at a light-input edge of the optically transmissive panel fromthe LED strip, the LED strip comprising a plurality of LEDs mounted tothe second portion of the frame adjacent the light-input edge of theoptically transmissive panel; and a first LED driver supported by thefirst portion of the frame and housed entirely within the first channeladjacent the first outer edge of the frame, wherein the first LED driveris configured to receive an AC input from an external AC power supplyand to provide a DC output to the LED strip.

One aspect of the disclosed technology relates a light fixture includinga frame having a thickness of no more than about 1.0 inches andincluding a first portion of the frame and a second portion of theframe, wherein the first portion of the frame defines a first channelbetween a first edge of an optically transmissive panel and a firstouter edge of the frame; a substantially flat light emitting diode (LED)panel disposed within the frame and having a first face that defines afirst plane and a second face that defines a second plane, wherein thesubstantially flat LED panel includes an LED strip and the opticallytransmissive panel, and the optically transmissive panel is configuredto distribute light received at a light-input edge of the opticallytransmissive panel from the LED strip, the LED strip comprising aplurality of LEDs mounted to the second portion of the frame adjacentthe light-input edge of the optically transmissive panel; and a firstLED driver supported by the first portion of the frame and housed withinthe first channel adjacent the first outer edge of the frame, wherein aportion of the LED driver is within at least one of the first plane andthe second plane, and wherein the first LED driver is configured toreceive an AC input from an external AC power supply and to provide a DCoutput to the LED strip.

One aspect of the disclosed technology relates a light fixture includinga frame having a thickness of no more than about 1.0 inches andincluding a portion of the frame that defines a channel between a firstedge of an optically transmissive panel and an outer edge of the frame;a substantially flat light emitting diode (LED) panel disposed withinthe frame, wherein the substantially flat LED panel includes an LEDstrip and the optically transmissive panel, wherein the opticallytransmissive panel is configured to distribute light received at alight-input edge of the optically transmissive panel from the LED strip,and wherein the LED strip comprises a plurality of LEDs arrayed in a rowsupported by an LED bar adjacent the light-input edge of the opticallytransmissive panel; and an LED driver supported by the portion of theframe and housed entirely within the channel adjacent the outer edge ofthe frame, wherein a portion of the LED driver is within a plane that isnormal to the LED bar and that contains the plurality of LEDs arrayed inthe row, and wherein the LED driver is configured to receive an AC inputfrom an external AC power supply and to provide a DC output to the LEDstrip.

The present application is directed to a light fixture including a lightemitting diode panel and associated driving circuitry. In accordancewith one aspect of the disclosed technology, the light fixture includespower circuitry sized and configured to be housed within the frame ofthe light fixture. In accordance with one aspect, the light fixture caninclude multiple configurations of light emitting diode (LED) arraysthat can be operated alternately. In accordance with another aspect, thelight fixture can include multiple drivers operatively coupled to a LEDarray, where the drivers can be selectively operated to drive the LEDarray.

One aspect of the disclosed technology relates to a light fixture thatincludes a frame; a light emitting diode (LED) panel disposed within theframe; and power circuitry disposed within the frame, the powercircuitry being configured to electrically couple the substantially flatLED panel to an external power supply.

According to one feature, the power circuitry is sized to be positionedwithin a channel defined by the frame.

According to one feature, the power circuitry includes driving circuitryconfigured to convert an AC input into a DC output suitable for poweringthe LED panel.

According to one feature, the power circuitry has a length and a width,wherein the length-to-width ratio is at least 5 to 1.

According to one feature, the power circuitry has a length and a width,wherein the length-to-width ratio is at least 10 to 1.

According to one feature, at least a portion of the frame defines afirst channel configured to support the power circuitry.

According to one feature, at least a portion of the frame is configuredto support an array of LEDs disposed adjacent to an edge of the frame.

According to one feature, the first channel is configured to support thearray of LEDs.

According to one feature, at least a portion of the frame defines asecond channel configured to support the array of LEDs.

According to one feature, at least a portion the frame is configured tosupport electrical connectors between the power circuitry and the arrayof LEDs.

According to one feature, the power circuitry includes an array ofcircuit modules supported by the first channel.

According to one feature, the first channel has a height of no more thanabout 0.5 inches.

According to one feature, the first channel has a width of no more thanabout 1.0 inches.

According to one feature, at least a portion of the frame defines asecond channel configured to support the power circuitry.

According to one feature, the power circuitry within the second channelhas a length of about 12 inches.

According to one feature, at least a portion of the frame defines athird channel configured to support an array of LEDs disposed adjacentat least one side of the frame.

According to one feature, the power circuitry includes a LED driverhaving a length, a width and a height, wherein the length is about 12inches, the width is about 1.0 inches and the height is about 0.5inches.

According to one feature, the LED panel is edge lit.

According to one feature, the LED panel includes a plurality of LEDsdisposed adjacent at least one edge of the frame.

According to one feature, the frame is rectangular and the LED panelincludes an array of LEDs incorporated into at least two sides of theframe.

According to one feature, the LED panel includes: anoptically-transmissive panel; and an array of LEDs disposed adjacent atleast one edge of the frame and disposed adjacent the opticallytransmissive panel.

According to one feature, the LED panel includes anoptically-transmissive panel; and an array of LEDs disposed across afirst surface of the optically-transmissive panel.

According to one feature, the array of LEDs is disposed acrosssubstantially the entire first surface of the optically-transmissivepanel.

According to one feature, the frame of the light fixture has a thicknessof no more than about 0.5 inches.

According to one feature, the frame of the light fixture has a thicknessof no more than about 1.0 inches.

According to one feature, the frame is rectangular and the LED panelincludes: a light guide plate; a first array of LEDs incorporated into afirst side of the frame adjacent a first side of the light guide plate,the first array of LEDs emitting light focused along a first direction;a second array of LEDs incorporated into a second side of the frameadjacent a second side of the light guide plate, the second array ofLEDs emitting light focused along a second direction that is oppositethe first direction; a first brightness enhancement film (BEF)positioned adjacent the light guide plate and configured to collimatelight emitted by the first array of LEDs; and a second BEF positionedadjacent the first BEF and configured to collimate light emitted by thesecond array of LEDs.

According to one feature, the power circuitry includes a controllerconfigured to control the intensity of the light emitted by the LEDpanel.

According to one feature, the LED panel includes: a first configurationof LEDs; and a second configuration of LEDs.

According to one feature, the power circuitry is configured to power thefirst configuration of LEDs for a first time period and to power thesecond configuration of LEDs for a second time period equal to the firsttime period.

According to one feature, the LED panel includes a third configurationof LEDS, wherein the power circuitry is configured to power the firstconfiguration of LEDs for a first time period, to power the secondconfiguration of LEDs for a second time period equal to the first timeperiod, and to power the third configuration of LEDs for a third timeperiod equal to the first time period.

According to one feature, the power circuitry is configured toalternatively power the first configuration of LEDs and the secondconfiguration of LEDs over a cyclical time period including the firsttime period and the second time period.

According to one feature, the first configuration of LEDs and the secondconfiguration of LEDs are arranged in an alternating arrangement.

According to one feature, the first configuration of LEDs is arranged ina first row and the second configuration of LEDs is arranged in a secondrow adjacent the first row.

According to one feature, the first configuration of LEDs and the secondconfiguration of LEDs are arranged in a first row and a second row belowthe first row.

According to one feature, the first configuration of LEDs and the secondconfiguration of LEDs are arranged in a pair of rows, wherein each rowof the pair of rows includes the first configuration of LEDs and thesecond configuration of LEDs arranged in an alternating arrangement

According to one feature, the first configuration of LEDs and the secondconfiguration of LEDs are arranged in a pair of rows in an alternatingarrangement.

According to one feature, the first configuration of LEDs is arranged ina first row on a first side of the frame and the second configuration ofLEDs is arranged in a second row on a second side of the frame oppositethe first side of the frame.

According to one feature, first configuration of LEDs includes a firstarray on a first side of the frame and a second array on a second sideof the frame opposite the first side of the light frame.

According to one feature, the second configuration of LEDs includes athird array on a third side of the frame and a fourth array on a fourthside of the frame opposite the third side of the light frame.

According to one feature, the first configuration of LEDs includes afirst array on a first side of the frame and a second array on a secondside of the frame adjacent the first side of the light frame.

According to one feature, the second configuration of LEDs includes athird array of LEDs on a third side of the frame opposite the first sideof the frame and a fourth array of LEDs on a fourth side of the frameopposite the second side of the frame.

According to one feature, the first configuration of LEDs and the secondconfiguration of LEDs are arranged in a pair of arrays on opposite sidesof the frame, wherein the first configuration of LEDs and the secondconfiguration of LEDs are arranged in an alternating arrangement in thepair of arrays on opposite sides of the light fixture.

According to one feature, the power circuitry comprises a first LEDdriver operatively coupled to the first configuration of LEDs and asecond LED driver operatively coupled to the second configuration ofLEDs.

According to one feature, the first LED driver is configured toselectively power the first configuration of LEDs and the second LEDdriver is configured to selectively power the second configuration ofLEDs

According to one feature, the power circuitry includes a controlleroperatively coupled to the first LED driver and the second LED driver,wherein the controller is configured to control the first LED driver andthe second LED driver to power the first configuration of LEDs for afirst time period and to power the second configuration of LEDs for asecond time period equal to the first time period.

According to one feature, the power circuitry includes a controlleroperatively coupled to the first LED driver and the second LED driver,wherein the controller is configured to monitor failure of the first LEDdriver and the second LED driver.

According to one feature, the power circuitry comprises a first LEDdriver operatively coupled to the first configuration of LEDs and thesecond configuration of LEDs, and a second LED driver operativelycoupled to the first configuration of LEDs and the second configurationof LED s.

According to one feature, the first LED driver is configured toselectively power the first configuration of LEDs and the secondconfiguration of LEDs, and the second LED driver is configured toselectively power the first configuration of LEDs and the secondconfiguration of LED s.

According to one feature, the power circuitry includes a controlleroperatively coupled to the first LED driver and the second LED driver,wherein the controller is configured to control the first LED driver andthe second LED driver to power the first configuration of LEDs for afirst time period and to power the second configuration of LEDs for asecond time period equal to the first time period.

According to one feature, the power circuitry includes a controlleroperatively coupled to the first LED driver and the second LED driver,wherein the controller is configured to monitor failure of the first LEDdriver and the second LED driver.

According to one feature, the controller is configured to selectivelyactivate the second LED driver to power the first configuration of LEDsand the second configuration of LEDs upon detection of failure ormalfunction by the first LED driver.

Another aspect of the disclosed technology relates to a light fixturethat includes a first set of light emitting diodes (LEDs); a second setof light emitting diodes (LEDs); an optically transmissive panel, eachof the first set of LEDs and the second set of LEDs being disposedadjacent to an edge of the optically transmissive panel; and drivingcircuitry operatively coupled to the first set of LEDs and the secondset of LEDs and an associated power supply, wherein the drivingcircuitry is configured to selectively power the first set of LEDs andthe second set of LEDs in an alternating manner.

According to one feature, the driving circuitry is configured to powerthe first set of LEDs for a first time period and to power the secondset of LEDs for a second time period equal to the first time period.

According to one feature, the light fixture includes a third set oflight emitting diodes (LEDs), and the driving circuitry is configured topower the first set of LEDs for a first time period, to power the secondset of LEDs for a second time period equal to the first time period, andto power the third set of LEDs for a third time period equal to thefirst time period.

According to one feature, the first set of LEDs and the second set ofLEDs are arranged in a single row in an alternating arrangement.

According to one feature, the first set of LEDs is arranged in a firstrow and the second set of LEDs is arranged in a second row adjacent thefirst row.

According to one feature, the first set of LEDs and the second set ofLEDs are arranged in a first row and a second row below the first row.

According to one feature, the first set of LEDs and the second set ofLEDs are arranged in a pair of rows, wherein each row of the pair ofrows includes the first set of LEDs and the second set of LEDs arrangedin an alternating arrangement

According to one feature, the first set of LEDs and the second set ofLEDs are arranged in a pair of rows in an alternating arrangement.

According to one feature, the first set of LEDs is arranged in a row ona first side of the optically transmissive panel and the second set ofLEDs is arranged in a row on a second side of the optically transmissivepanel opposite the first side of the optically transmissive panel.

According to one feature, the first set of LEDs includes a first arrayon a first side of the light fixture and a second array on a second sideof the light fixture opposite the first side of the light fixture.

According to one feature, the second set of LEDs includes a third arrayon a third side of the light fixture and a fourth array on a fourth sideof the light fixture opposite the third side of the light fixture.

According to one feature, the first set of LEDs includes a first arrayon a first side of the light fixture and a second array on a second sideof the light fixture adjacent the first side of the light fixture.

According to one feature, the second set of LEDs includes a third arrayof LEDs on a third side of the light fixture opposite the first side ofthe light fixture and a fourth array of LEDs on a fourth side of thelight fixture opposite the second side of the light fixture.

According to one feature, the first set of LEDs and the second set ofLEDs are arranged in a pair of arrays on opposite sides of the lightfixture, wherein the first set of LEDs and the second set of LEDs arearranged in an alternating arrangement in the pair of arrays on oppositesides of the light fixture.

According to one feature, the driving circuitry comprises a first LEDdriver operatively coupled to the first set of LEDs and a second LEDdriver operatively coupled to the second set of LEDs.

According to one feature, the first LED driver is configured toselectively power the first set of LEDs and the second LED driver isconfigured to selectively power the second set of LEDs.

According to one feature, the driving circuitry includes a controlleroperatively coupled to the first LED driver and the second LED driver,wherein the controller is configured to control the first LED driver andthe second LED driver to power the first set of LEDs for a first timeperiod and to power the second set of LEDs for a second time periodequal to the first time period.

According to one feature, the driving circuitry includes a controlleroperatively coupled to the first LED driver and the second LED driver,wherein the controller is configured to monitor failure of the first LEDdriver and the second LED driver.

According to one feature, the driving circuitry comprises a first LEDdriver operatively coupled to the first set of LEDs and the second setof LEDs, and a second LED driver operatively coupled to the first set ofLEDs and the second set of LEDs.

According to one feature, the first LED driver is configured toselectively power the first set of LEDs and the second set of LEDs, andthe second LED driver is configured to selectively power the first setof LEDs and the second set of LEDs.

According to one feature, the driving circuitry includes a controlleroperatively coupled to the first LED driver and the second LED driver,wherein the controller is configured to control the first LED driver andthe second LED driver to power the first set of LEDs for a first timeperiod and to power the second set of LEDs for a second time periodequal to the first time period.

According to one feature, the driving circuitry includes a controlleroperatively coupled to the first LED driver and the second LED driver,wherein the controller is configured to monitor failure of the first LEDdriver and the second LED driver.

According to one feature, the controller is configured to activate thesecond LED driver to power the first set of LEDs and the second set ofLEDs upon detection of failure of the first LED driver.

According to one feature, the controller is configured to selectivelyactivate the second LED driver to power the first set of LEDs and thesecond set of LEDs upon detection of failure or malfunction by the firstLED driver.

According to another aspect of the disclosed technology, a light fixtureincludes an array of light emitting diodes (LEDs); and driving circuitryoperatively coupled to the array of LEDs, wherein the driving circuitryincludes: a first LED driver selectively operatively coupled to thearray of LEDs and a second LED driver selectively operatively coupled tothe array of LEDs; and a controller operatively coupled to the first LEDdriver and the second LED driver, wherein the controller is configuredto selectively activate the second LED driver to power the array of LEDsupon detection of failure or malfunction by the first LED driver.

According to one feature, the controller is configured to selectivelyactivate the first LED driver to power the array of LEDs upon detectionof failure of malfunction by the second LED driver.

Another aspect of the disclosed technology relates to a light fixturethat includes a frame; a light emitting diode (LED) panel disposedwithin the frame, wherein the LED panel includes: a first configurationof light emitting diodes (LEDs); and a second configuration of lightemitting diodes (LEDs); and driving circuitry operatively coupled to thefirst configuration of LEDs and the second configuration of LEDs,wherein the driving circuitry is configured to selectively power thefirst configuration of LEDs and the second configuration of LEDs in analternating manner.

Another aspect of the disclosed technology relates to a method forextending rated life of a light emitting diode (LED) light fixture,where the LED light fixture having at least one array of LEDs. Themethod includes providing a first LED driver selectively operativelycoupled to the at least one array of LEDs; providing a second LED driverselectively operatively coupled to the at least one array of LEDs;electrically coupling the first LED driver to the at least one array ofLEDs and; monitoring the first LED driver for failure, malfunction orreduced performance; if failure, malfunction or reduced performance isdetected for the first LED driver, electrically coupling the second LEDdriver to the at least one array of LEDs and electrically decoupling thefirst LED driver from the at least one array of LEDs.

Another aspect of the disclosed technology relates to a method ofextending rated life of a light emitting diode (LED) light fixture. Themethod includes providing a first configuration of LEDs; providing asecond configuration of LEDs; and selectively powering the firstconfiguration of LEDs and the second configuration of LEDs in analternating manner.

These and further features of the present invention will be apparentwith reference to the following description and attached drawings. Inthe description and drawings, particular embodiments of the inventionhave been disclosed in detail as being indicative of some of the ways inwhich the principles of the invention may be employed, but it isunderstood that the invention is not limited correspondingly in scope.Rather, the invention includes all changes, modifications andequivalents coming within the spirit and terms of the claims appendedthereto.

Features that are described and/or illustrated with respect to oneembodiment may be used in the same way or in a similar way in one ormore other embodiments and/or in combination with or instead of thefeatures of the other embodiments.

It should be emphasized that the term “comprises/comprising” when usedin this specification is taken to specify the presence of statedfeatures, integers, steps or components but does not preclude thepresence or addition of one or more other features, integers, steps,components or groups thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the invention can be better understood with reference tothe following drawings. The components in the drawings are notnecessarily to scale, emphasis instead being placed upon clearlyillustrating the principles of the present invention. Likewise, elementsand features depicted in one drawing may be combined with elements andfeatures depicted in additional drawings. Moreover, in the drawings,like reference numerals designate corresponding parts throughout theseveral views.

FIG. 1 is a diagrammatic illustration of a LED panel light fixture inaccordance with one aspect of the disclosed technology;

FIG. 2 is a diagrammatic illustration of a LED panel light fixture inaccordance with one aspect of the disclosed technology;

FIG. 3 is a diagrammatic illustration of a LED panel light fixture inaccordance with one aspect of the disclosed technology;

FIG. 4 is a perspective view of a LED panel light fixture in accordancewith one aspect of the disclosed technology;

FIG. 5 is a rear view of a LED panel in accordance with one aspect ofthe disclosed technology;

FIG. 6 is a rear perspective view of a LED panel in accordance with oneaspect of the disclosed technology;

FIG. 7 is a diagrammatic illustration of a substantially flat LED panelin accordance with one aspect of the disclosed technology;

FIG. 8 is a diagrammatic illustration of a substantially flat LED panelin accordance with one aspect of the disclosed technology;

FIG. 9 is a diagrammatic illustration of a substantially flat LED panelin accordance with one aspect of the disclosed technology;

FIG. 9A is a diagrammatic illustration of a substantially flat LED panelin accordance with one aspect of the disclosed technology;

FIG. 9B is a diagrammatic illustration of a substantially flat LED panelin accordance with one aspect of the disclosed technology;

FIG. 10 is shows an exploded view of an optical stack of a LED panel inaccordance with one aspect of the disclosed technology;

FIG. 11 is shows an exploded view of an optical stack of a LED panel inaccordance with one aspect of the disclosed technology;

FIG. 12 is a rear perspective view of a LED panel in accordance with oneaspect of the disclosed technology;

FIG. 13 is a rear view of a portion of a LED panel in accordance withone aspect of the disclosed technology;

FIG. 14 is a diagrammatic illustration of a portion of a frame housingpower circuitry in accordance with one aspect of the disclosedtechnology;

FIG. 14A is a diagrammatic illustration of a portion of a frame housingpower circuitry in accordance with one aspect of the disclosedtechnology;

FIG. 15 is a rear view of a portion of a LED panel in accordance withone aspect of the disclosed technology;

FIG. 16 is a diagrammatic illustration of a portion of a frame inaccordance with one aspect of the disclosed technology;

FIG. 17 is a perspective view of a portion of a LED panel in accordancewith one aspect of the disclosed technology;

FIG. 18 is a perspective view of a portion of a LED panel in accordancewith one aspect of the disclosed technology;

FIG. 19 is a perspective view of a portion of a LED panel in accordancewith one aspect of the disclosed technology;

FIG. 20 is a perspective view of a portion of a frame in accordance withone aspect of the disclosed technology;

FIG. 21 is a perspective view of a portion of a frame in accordance withone aspect of the disclosed technology;

FIG. 22 is a perspective view of a portion of a LED panel in accordancewith one aspect of the disclosed technology;

FIG. 23 is a perspective view of a portion of a LED panel in accordancewith one aspect of the disclosed technology;

FIG. 24 is a diagrammatic illustration of the light fixture inaccordance with one aspect of the disclosed technology;

FIG. 25 is a diagrammatic illustration of the light fixture inaccordance with one aspect of the disclosed technology;

FIG. 26 is a diagrammatic illustration of the light fixture inaccordance with one aspect of the disclosed technology;

FIG. 27 is a diagrammatic illustration of the light fixture inaccordance with one aspect of the disclosed technology;

FIG. 28 is a diagrammatic illustration of the light fixture inaccordance with one aspect of the disclosed technology;

FIG. 29 is a diagrammatic illustration of a LED assembly in accordancewith one aspect of the disclosed technology;

FIG. 30 is a diagrammatic illustration of a LED assembly in accordancewith one aspect of the disclosed technology;

FIG. 31 is a diagrammatic illustration of a LED assembly in accordancewith one aspect of the disclosed technology;

FIG. 32 is a diagrammatic illustration of the light fixture inaccordance with one aspect of the disclosed technology;

FIG. 33 is a diagrammatic illustration of the light fixture inaccordance with one aspect of the disclosed technology;

FIG. 34 is a diagrammatic illustration of the light fixture inaccordance with one aspect of the disclosed technology;

FIG. 35 is a diagrammatic illustration of the light fixture inaccordance with one aspect of the disclosed technology.

DETAILED DESCRIPTION

To illustrate aspects of the disclosed technology in a clear and concisemanner, the drawings may not necessarily be to scale and certainfeatures may be shown in somewhat schematic form.

A growing sophistication about the economics of lighting has emerged,and with it, recognition that luminous efficacy, or lumens per watt, isnot the only important variable in designing and maintainingcost-effective, quality lighting. Lamp life is another importantconsideration. Service life is increasingly a driver in the developmentof new lamps and lighting systems. More lamp manufacturers are usinglife to distinguish their own products from those of their competitors.

Lamp packaging typically states the manufacturer's determination of lamplife, called rated life, usually in hours. The most straightforwardinterpretation of these ratings is arguably that they tell us how longthe lamp will operate before it fails (“burns out”). But the definitionof life is different for different lamp types.

Incandescent lamp life is measured by operating a sample of lampscontinuously in a specified position and at a specified voltage. Thenumber of burning hours at which half the lamps have failed isconsidered the rated life of the lamps. Fluorescent lamps can be testedwhile operating at a specified temperature (e.g., 25° C./77° F.) on acontinuous 3-hour-on, 20-minute-off cycle, with a standard ballastcircuit that controls the current. As with incandescent lamps, ratedlife is the elapsed number of operating hours at which half of the lampsin a sample have burned out.

Light Emitting Diode (LED) light sources typically do not fail in thesense that other sources do. Over time, however, their light output candecrease until they are no longer useful for a given purpose. LEDs oftenlast hundreds of times longer than incandescent bulbs and fluorescenttubes—up to 100,000 hours.

Because LEDs require much smaller voltages of direct current, anotherfactor that reduces the apparent long life of LEDs is the need forauxiliary electronics and equipment to house and operate these sources.Because electrical power commercially available in the United States isin the form of alternating current, LEDs require direct currentconverters. Such devices may have rated lives significantly shorter thanthe LEDs with which they are used. Higher voltage and high temperaturescan also increase lumen depreciation in LEDs.

In addition, while some substantially flat LED panel lighting fixtureshave been employed, these lighting fixtures make use of an AC-to-DCpower converter module external to the fixture (e.g., extending outwardfrom the back surface of the fixture). A power converter module externalto the lighting fixture limits design flexibility in integrating LEDflat panel fixtures or luminaires into a range of applications, and addscomplexity to installation. For example, in installations in which alighting fixture would be surface mounted in a visible location, therewould be no out-of-view place for ancillary equipment such as a powerconverter.

The present disclosure recognizes shortcomings associated withconventional fluorescent lamp and incandescent lamp lighting systems. Inaddition, the present disclosure recognizes potential shortcomings withLED-based lighting assemblies and associated power circuitry, andprovides an improved lighting fixture and associated power circuitry.

The present disclosure recognizes that the operating life on an entirelighting product or system must be considered, rather than just thepotentially-promising long-rated life of LEDs within the lightingproduct or system. Besides improving the effects of lumen depreciationof LEDs, the present disclosure reduces the likelihood of catastrophicfailure of other parts of the lighting product or system, including inparticular a power supply or driver for the LEDs. As is described morefully below, the present application is directed to a light fixtureincluding a light emitting diode panel and associated driving circuitry.In accordance with one aspect of the disclosed technology, the lightfixture includes power circuitry configured to be housed within theframe of the light fixture. In accordance with one aspect, the lightfixture can include multiple configurations of light emitting diode(LED) arrays that can be operated alternately. In accordance withanother aspect, the light fixture can include multiple driversoperatively coupled to a LED array, where the drivers can be selectivelyoperated to drive the LED array. In accordance with another aspect, theoutput of LED arrays can be adjusted to maintain lumen brightness anduniformity.

Referring now to FIGS. 1-9B, an exemplary embodiment of a light fixture10 having a light emitting diode (LED) panel 12 is provided. In oneembodiment, the LED panel 12 is a substantially flat LED panel (alsoreferred to simply as a LED panel). The term “substantially flat LEDpanel” as used in connection with the description of the variousembodiments, is meant to include LED panels having a thickness that issubstantially less than the length and width of the panel. The term “LEDpanel fixture,” as used in connection with the description of thevarious embodiments, denotes a light fixture 10 that incorporates asubstantially flat LED panel. LED panel fixtures may be of slightlynon-uniform thickness due to the configuration of the LED panel or ofanother part of the light fixture 10. For example, an LED panel fixturecan include a frame (designated generally as 14) having a thickness thatis greater than the thickness of the LED panel 12.

As shown in the various figures, the light fixture 10 includes a frame14 that surrounds the LED panel 12. The frame 14 provides structuralsupport, contains components of the LED panel fixture such as arrays,strips, or bars of LEDs 20 and the power circuitry (also referred to asdriving circuitry, and as LED power circuitry or LED driving circuitry)(designated generally as 16), and provides heat dissipation. As isdescribed more fully below, the frame can be configured to house orotherwise support LED power circuitry as well as associated wiring andelectrical connections between the power circuitry and the LED arrays.

The light fixture 10, including the LED panel 12 may take on a varietyof dimensions and form factors, including, but not limited to,rectangular, other polygonal (e.g., octagonal), circular and ellipticalform factors. For example, the light fixture can be square (see FIG. 1)with a size of approximately nine inches by nine inches, approximatelytwelve inches by twelve inches, or approximately twenty-four inches bytwenty-four inches. By way of example, the light fixture 10 also can berectangular with a size of approximately one foot by four feet (1 foot×4feet) (see FIG. 2) or a size of approximately two feet by four feet (2feet×4 feet) (see FIG. 3), corresponding to exemplary lower dimensionsof standard fluorescent ceiling troffers. In another embodiment, thelight fixture 10 can be sized to standard lengths for under counter orunder cabinet lighting applications (e.g., twelve inches, eighteeninches, twenty-four inches, thirty-six inches, etc.). The LED panel cantake on any lateral size, while maintaining a relatively smallthickness, without departing from the scope of the disclosed technology.This versatility in sizing provides enhanced flexibility in use inconnection with a variety of applications.

As noted above, in accordance with one exemplary embodiment, the lightfixture 10 can include a frame 14, a substantially flat LED panel 12disposed within the frame 14 and power circuitry 16 disposed orotherwise housed within the frame 14. The power circuitry 16 isconfigured to electrically couple the LED panel 12 to an external powersupply (not shown), for example, via a suitable electrical connectorsuch as a plug or socket connector 18. It will be appreciated that theLED panel fixture can be configured to provide bright, uniform light ina relatively thin package. For example, in accordance with oneembodiment, the substantially flat LED panel 12 can have a thickness ofless than about 1.0 inches. In accordance with another embodiment, thesubstantially flat LED panel 12 can have a thickness of less than about0.5 inches. In accordance with one exemplary embodiment, the frame 14can be made up of four segments having mitered joints. Alternatively,the frame 14 can be formed from two pieces (e.g., a top piece and abottom piece) snapped or otherwise joined together. The frame can defineor otherwise include stand-offs on the back of the frame (e.g., forproviding ventilation when the frame is surface mounted to a supportsurface).

Referring now to FIGS. 10-11, and with continued reference to FIGS. 1-9,exemplary embodiments, in which the LED panel includes a plurality oflayers along with edge lighting disposed adjacent to at least one edgeof the frame, are provided. In the illustrated exemplary embodiments,the LED panel includes an optically-transmissive panel 22, e.g., a lightguide plate or other polycarbonate or acrylic plate configured toproduce even distribution of light received at edges of theoptically-transmissive panel 22. An array of LEDs (designated generallyas 20) can be disposed adjacent at least one edge of the frame 14 andthe optically transmissive panel 22. For example, a strip of LEDs 20 maybe supported adjacent to one edge of the frame 14 (e.g., disposed withina channel in the frame) and adjacent to one edge of theoptically-transmissive panel 22. Alternatively, the LED panel 12 caninclude strips, arrays or configurations of LEDs 20 incorporated into orat least partially supported by two edges of the frame 14. (Referencesin this disclosure to LEDs 20 being supported by, incorporated into oradjacent an edge of the frame includes the LEDs being supported by awall of a channel located at the edge of the frame, wherein the channelwall is offset from the edge of the frame by the width of the channel).

The strips, arrays or configurations of LEDs can be mounted to the frameusing one of a number of suitable methods. For example, the LED stripsor arrays 20 can be secured to a portion of the frame (e.g., within achannel in the frame) using a suitable adhesive or suitable fasteners.It will be appreciated that the LED strips or arrays 20 can be mountedto the frame in a way that controls the dissipation of heat from the LEDstrips or arrays to the frame. For example, it can be desirable to usethe frame to dissipate some heat from LED arrays 20, while limiting theamount of heat passing to the frame to prevent the frame from becomingtoo warm. In accordance with one exemplary embodiment, a suitableadhesive can be used to allow a limited amount of heat transfer from theLED arrays 20 to the frame 14. Alternatively, metal fasteners (or directcontact with the frame) can be used to facilitate a greater degree ofheat transfer from the LED arrays to the frame.

In yet another exemplary embodiment in which the light fixture 10 has arectangular form factor, the LED panel 12 can include strips, arrays orconfigurations of LEDs 20 incorporated into or at least partiallysupported by all four edges of the frame 14. The LEDs can be sized andpositioned such that the “emission dimension” of the LED elements hasthe same thickness or slightly less thickness than the thickness of thelight input edge of the optically-transmissive panel, thereby allowingfor an extremely thin profile. Not shown in the drawings, the LEDs mayinclude optical coupling structures such as lenses or reflectors thatdirect light emitted by the LEDs into an edge of optically-transmissivepanel 22.

The LED panel 12 can include a diffuser film 24 disposed on a first sideof the optically-transmissive panel 22, e.g., below the opticallytransmissive panel 22 when the fixture is mounted horizontally for aceiling lighting application. The outer diffuser film 24 is configuredto provide uniform light output, and can be made of any suitablematerial. For example, for outdoor applications, the outer diffuser film24 can be a weatherable film. The outer diffuser film 24 can beconfigured as a soft film or as a hard, abrasion-resistant filmdepending upon the particular application. The outer diffuser film 24can be made waterproof or moisture proof depending upon the desiredapplication.

The LED panel 12 can include a brightness enhancement film (BEF) 26disposed on a second side of the optically-transmissive panel 22, e.g.,above the optically-transmissive panel 22 when the fixture is mountedhorizontally for a ceiling lighting application. The brightnessenhancement film 26 can be configured to collimate light along avertical axis to improve the overall light output from the LED panel 12.In accordance with one embodiment, the LED panel can be configured toinclude multiple BEFs optimized for the particular arrangement of LEDsalong one or more edges of the LED panel. In this exemplary embodiment,the LED panel can include an optically-transmissive panel in the form ofa light guide plate with a first array of LEDs incorporated into a firstside of the frame adjacent a first side of the light guide plate, thefirst array of LEDs emitting light focused along a first direction, anda second array of LEDs incorporated into a second side of the frameadjacent a second side of the light guide plate, the second array ofLEDs emitting light focused along a second direction that is oppositethe first direction. The substantially flat LED panel can include afirst brightness enhancement film (BEF) positioned adjacent the lightguide plate and configured to collimate light emitted by the first arrayof LEDs, and a second BEF positioned adjacent the first BEF andconfigured to collimate light emitted by the second array of LEDs.

The LED panel 12 can include a reflector 28 positioned on the other sideof the BEF 26 (e.g., above the BEF 26) when the fixture is mountedhorizontally (e.g., for a ceiling lighting application). The reflector28 is configured and position to return a portion of the light emittedby the optically-transmissive panel 22 in a direction opposite theintended output direction, thereby providing enhanced total lightoutput. In the illustrated exemplary embodiments, the substantially flatLED panel 12 includes a backing 30, e.g., a sheet metal backing disposedadjacent the other side of the reflector 28. A sheet metal backing 30 incombination with a metallic (e.g., aluminum) frame 14 can provideexcellent dissipation of heat generated by the LEDs.

While aspects of the disclosed technology have been described withrespect to LED strips or arrays disposed adjacent to edges of the frameand the optically-transmissive panel, it will be appreciated that otherconfigurations may be employed without departing from the scope of thepresent invention. For example, FIG. 9B shows an embodiment in which anarray of LEDs (e.g., a full array of LEDs) is disposed across most orsubstantially all of the area of an optically-transmissive panel, whilereceiving power from edge-mounted power circuitry within the frame ofthe flat panel lighting fixture. For example, the panel can incorporaterows of LEDs at one face of the optically-transmissive panel, whereinthe LEDs in each row are electrically coupled by a power line to adriver located at the edge of the LED fixture.

With continued reference to FIGS. 1-9B, and turning now to FIGS. 12-23,in accordance with one exemplary embodiment, the light fixture 10includes power circuitry 16 disposed or otherwise housed within theframe 14, where the power circuitry 16 is configured to electricallycouple the LED panel 12 to an external power source (e.g., via asuitable electrical connector 18). It will be appreciated that thisembodiment serves to provide an LED panel fixture with an extremely thinform factor that can be easily mounted to a flat surface, such as awall, an underside of a cabinet or the like. As shown in FIGS. 7-9, thelight fixture 10 can be configured to include first and second LEDstrips, bars, arrays or configurations (designated generally as 20)disposed on opposite sides of the frame 14, along with power circuitryin the form of a pair of LED drivers 16 positioned in one or both of theremaining sides of the rectangular frame. The illustrated embodimentshows a first LED driver 16 electrically coupled to and configured tocontrol a first LED array (e.g., an LED strip 20), along with a secondLED driver 16 coupled to and configured to control the second LED array(e.g., an LED strip).

As noted above, the light fixture includes power circuitry 16 disposedwithin or otherwise housed by the frame, where the power circuitry 16 isconfigured to electrically couple the LED panel 12 to an external powersource. It will be appreciated that the power circuitry will beconfigured to have a relatively long and narrow form factor, allowing itto be housed within a portion of a frame. FIGS. 14-18 show exemplaryembodiments of the power circuitry 16, or portions of the powercircuitry disposed or otherwise housed within a portion the frame 14.For example, in accordance with one exemplary embodiment, the powercircuitry (or component boards of the power circuitry) can have a lengthand a width, where the length-to-width ratio is at least 5-to-1. Inaccordance with another exemplary embodiment, the power circuitry canhave a length-to-width ratio of at least 10-to-1.

The frame 14 can be configured to define or otherwise provide one ormore channels to support aspects of the power circuitry, the associatedwiring as well as LED arrays or bars. For example, a portion of theframe may be configured to define a channel 40 (e.g., a channeldesignated as a first channel or a second channel) sized to house aportion of the power circuitry 16. For example, in accordance with oneembodiment, the first channel 40 within a portion of the frame can beconfigured to house power circuitry (e.g., LED driver circuitry) havingdimensions of approximately twelve inches in length, approximately oneinch of width and approximately one half inch in height. It will beappreciated that the disclosed technology is not limited to theseexemplary dimensions. The first channel 40 can take on other dimensionswithout departing from the scope of the disclosed technology.

Such compact power and control circuitry can be obtained by employingminiaturized power and/or control boards. For example, a programmablelogic controller (PLC) motherboard can serve as a real-time clock withtiming control logic to regulate operation of the LED arrays. As isdiscussed more fully below, multiple arrays, sets or configurations ofLEDs can be operated in an alternating manner according to apredetermined timing sequence. This motherboard may operate incoordination with one or more daughterboards, which are disposed orotherwise housed within the frame (e.g., within a first or secondchannel defined by a portion of the frame) to provide additionalfunctionality. For example, a sensor module can process signals from oneor more sensors within the light fixture (e.g., a sensor to determinethe intensity and/or color temperature of light being emitted by thelight fixture) (see, for example, FIGS. 22-23). Output from thesesensors can be used, for example, to control the output intensity of thelighting fixture in the case of lumen depreciation for some or all ofthe LEDs within the lighting fixture.

It will be appreciated that various sensors can be employed withoutdeparting from the scope of the disclosed technology. For example,infrared sensors may be used for remote control dimming. Also, ambientlight sensors may be employed to provide automatic adjustment todimming. It also will be appreciated that the light fixture can beconfigured to receive external inputs to control operation, such assignals from an associated security camera or motion sensor system

Multiple control modules may be distributed within the frame forefficient use of space. For example, two primary drivers may be disposedor otherwise housed at opposite edges of the frame and one or moreinput/output modules can be housed at a transverse edge of the frame. Asshown in FIG. 14A, the use of miniaturized circuit elements permitsmultiple power supply or control modules to be arrayed within a givenchannel 40 of the frame 14. Three power supply modules 16A, 16B, and 16Care arrayed within the channel. As shown these are separate circuitelements, but multiple power supply or control modules also can beintegrated on a single circuit board. Respective power supply circuitscan be electrically coupled to different sets of LEDs within an array ofLEDs (not shown in FIG. 14A). This arrangement permits the DC voltageand current output specifications of each power supply circuit to bematched to input requirements of a subset of the LEDs within the LEDarray, while making efficient use of limited space within frame 14.Further, this arrangement can facilitate under-driving an array of LEDsto allow for increased driving in the case of lumen depreciation.

In accordance with one exemplary embodiment, the frame or a portion ofthe frame 14 can be configured to define another channel 42 (e.g., achannel designated as a first channel or a secondary channel) forhousing wiring or other electrical connectors associated with the lightfixture. For example, as shown in FIGS. 16-17, portions of the frame caninclude a channel 42 to support a number of wires connecting the LEDarrays to the driving circuitry. It will be appreciated that given thepotentially limited cross-sectional dimensions of the channel in certainportions of the frame or all of the frame, it might be undesirable toroute wiring or cables alongside circuit boards associated with thepower circuitry. In this situation, a channel can be defined to houseembedded conductive traces to conserve space within the frame. In thisexemplary embodiment, cables or other conventional wiring can be used atother locations around the frame, such as interconnecting an LED bar anddriving circuitry at a corner of the frame or at another area in theframe where power circuitry or driver circuitry is not present.

It will be appreciated that the driving circuitry can be tailored orotherwise customized to support the relatively long, but narrow,geometry of the driving circuitry. For example, space-sensitivecomponents, such as capacitors and the like, can be oriented along thelong direction of the power circuitry footprint. In addition, printedcircuit boards associated with the power circuitry can be configured toinclude multi-layers in which conductive layers and/or conductive tracesare stacked between insulating material. In addition as noted above,multiple circuit modules can be arrayed at a given channel or edge areaof frame 14.

In accordance with one exemplary embodiment, the frame or a portion ofthe frame can be configured to yet another channel 44 (e.g., a channeldesignated as a third channel) for housing a supporting arrays or stripsof LEDs 20.

It will be appreciated that housing the power circuitry within the framecan provide an LED panel fixture with an extremely thin form factor thatcan be easily mounted to a flat surface, such as a wall, an underside ofa cabinet or the like. As discussed above, the light fixture 10 can beconfigured to include first and second LED strips or bars 20 disposed onopposite sides of the frame 14, along with power circuitry in the formof a pair of LED drivers positioned in one or both of the remainingsides of the rectangular frame. The illustrated exemplary embodimentsshows a first LED driver electrically coupled to and configured tocontrol a first LED array along with a second LED driver coupled to andconfigured to control the second LED array.

FIG. 9 shows an alternative light fixture 10 with the first and secondLED arrays disposed on opposite sides of the frame 14 (e.g., on a topside of the frame and a bottom side of the frame in the orientationprovided in the figure), and with a pair of LED drivers positioned onboth remaining sides of the frame.

In FIG. 8 and FIG. 9, LED strips or bars 20 are located at differentsides of the frame 14 than LED drivers 16. As seen in FIG. 9A, it isalso possible to locate the LED drivers 16 on the same sides of theframe as the LED strips 20. This arrangement makes less efficient use ofthe space at the edges of frame 14, but may simplify electricalconnection of drivers 16 to LED strips 20.

Turning now to FIGS. 24-35, another aspect of the disclosed technologywill be described in greater detail. In accordance with one exemplaryembodiment, the light fixture can include multiple sets orconfigurations of LEDs. For example, the light fixture can be configuredto include a first set or configuration of LEDs 20 a and a second set orconfiguration of LEDs 20 b along with power circuitry (also referred toas driving circuitry) 16 operatively coupled to the first set of LEDs 20a and the second set of LEDs 20 b and an associated power supply(designated generally as 50), for example, a standard AC power supplyfound in a home or office setting, wherein the driving circuitry 16 isconfigured to selectively power the first set of LEDs 20 a and thesecond set of LEDs 20 b in an alternating manner.

In accordance with one embodiment (see FIGS. 25-26, and also FIG. 34),the power circuitry 16 can include a first driver 52 operatively coupledto the first LED configuration 20 a and a second driver 54 operativelycoupled to the second LED configuration 20 b. The power circuitry 16 caninclude a controller 56 operatively coupled to the first driver 52 andthe second driver 54, and configured to selectively operate the firstdriver 52 and the second driver 54 to control the first configuration ofLEDs 20 a and the second configuration of LEDs 20 b in a desired manner.FIG. 27 shows another exemplary embodiment in which switching circuitry58 is operatively coupled to the first driver 52 and the second driver54, and configured to selectively activate the first configuration ofLEDs 20 a and the second configuration of LEDs 20 b. FIG. 28 shows yetanother exemplary embodiment in which the controller 56 is operativelycoupled to the first driver 52 and the second driver 54 to selectivelycontrol operation of the first driver 52 and the second driver 54, aswell as monitor the first driver 52 and the second driver 54 to ensurethat the respective drivers are functioning properly. This embodimentwill be discussed in greater detail below.

In accordance with one embodiment, the first set or configuration ofLEDs 20 a and the second set or configuration of LEDs 20 b are drivenalternately. For example, while the first configuration of LEDs 20 a isactive, the second configuration of LEDs 20 b can be set to inactive andvice versa. In a preferred embodiment, the first and secondconfigurations of LEDs can be driven cyclically, for example, repeatedover periods of time where the “on” cycle time for the first set of LEDsis identical or substantially identical to the “on” cycle time for thesecond set of LEDs. It will be appreciated that permitting the LEDsadequate time to cool can extend the operating life of the LEDs, therebypotentially extending the operating life of the light fixture. It alsowill be appreciated that various timing cycles can be implemented withinthe scope of the disclosed technology. For example, in accordance withone exemplary embodiment, the first set of LEDs 20 a can be on for atwenty-four hour period and off for the next twenty-four hour period,where the second set of LEDs 20 b is on.

It will be appreciated that the first and second configurations of LEDscan be implemented in a number of ways without departing from the scopeof the disclosed technology. For example, as shown in FIG. 29, the firstconfiguration of LEDs 20 a and the second configuration of LEDs 20 b canbe arranged in a single strip or bar in which a single row of LEDelements are arrayed in an alternating arrangement (e.g., A B A Barrangement, where A corresponds to an LED within the first LEDconfiguration 20 a and B corresponds to an LED within the second LEDconfiguration 20 b).

Alternatively, as shown in FIG. 30, the LEDs may be disposed in orotherwise arranged in a two-strip bar in which the first configurationof LEDs 20 a is included along the top row and the second configurationof LEDs 20 b is included along the bottom row. In yet anotherembodiment, as shown in FIG. 31, the LEDs can be arranged in a two-stripor two-row formation such that the first strip includes alternatingarrangements of LEDs from the first configuration of LEDs 20 a and thesecond configuration of LEDs 20 b, and the second row of LEDs includesalternating arrangements from the first configuration of LEDs 20 a andthe second configuration of LEDs 20 b. It will be appreciated that inthese two-row arrangements, the traditional two-wire power supply for asingle row of LEDs operated together would be replaced by at least afour-wire power supply.

In yet another exemplary embodiment, as shown in FIG. 32, the lightfixture can be configured to have a first row of LEDs disposed on oneside of the frame and a second set of LEDs disposed on an opposite sideof the frame where the first set of LEDs and the second set of LEDs aredriven alternately according to a predetermined time cycle. In yetanother alternative embodiment, the first set of LEDs 20 a can include arow or array of LEDs on one side of the frame and another row or arrayof LEDs on the opposite side of the frame. In this embodiment, thesecond set of LEDs can be configured to include a first row of LEDs onone side of the frame disposed between the two sides used for the firstset. In yet another exemplary embodiment, the light fixture can includea first array of LEDs having alternating LEDs from the first set and thesecond set, with a mirror image configuration on the opposite side ofthe frame.

In accordance with yet another aspect of the disclosed technology, thelight fixture can be configured to include multiple drivers per LEDconfiguration. For example, as shown in FIG. 33, in a simple case of asingle LED configuration 20, a first driver 52 and a second driver 54can be selectively operatively coupled to the LED configuration 20together with appropriate switching or controlling circuitry 56. In thisexemplary embodiment, a first driver 52 would be selected toelectrically couple the LED configuration to the power supply 50. Faultdetection circuitry (e.g., incorporated into the controller 56) can beemployed to determine whether the first driver 52 is operating properly.If a fault condition occurs with the first driver 52, the controller orswitching circuitry 56 can then switch over to the second driver 54 suchthat the second driver 54 electrically couples the LED configuration 20to the associated power supply 50.

In accordance with another aspect of the disclosed technology, the lightfixture can incorporate more than two configurations of LEDs, with arespective driver for each configuration of LEDs. For example in FIG.35, the power circuitry 16 can include a first driver 52 operativelycoupled to the first LED configuration 20 a, a second driver 54operatively coupled to the second LED configuration 20 b, and a thirddriver 60 operatively coupled to the third LED configuration 20 c. Thepower circuitry 16 can include a controller 56 operatively coupled tothe first driver 52, the second driver 54 and the third driver 60, andconfigured to selectively operate the first driver 52, the second driver54 and the third driver 56, thereby to control the first, second andthird configurations of LEDs 20 a, 20 b, 20 c in a desired manner. In apreferred embodiment, the first, second and third configurations of LEDscan be driven cyclically, for example, repeated over periods of timewhere the “on” cycle time for the first set of LEDs is identical orsubstantially identical to the “on” cycle time for the second set ofLEDs and the “on” cycle time for the third set of LEDs. For example,while the first configuration of LEDs 20 a is active, the secondconfiguration of LEDs 20 b and third configuration of LEDs can be set toinactive. Alternatively, two configurations of LEDs can be set to activeduring a given time period, while the third can be set to inactive. Inthe case of more than two configurations of LEDs, it will be appreciatedthat the configurations can be arranged in a manner consistent with thedescriptions of two configurations above. For example, the first, secondand third configurations of LEDs can be arranged in an alternatingmanner and/or in alternating strips or arrays.

In the case of the light fixture having multiple LED configurations, forexample, a first LED configuration 20 a and a second LED configuration20 b, the first driver can be selectively operatively coupled to boththe first LED configuration and the second LED configuration. Similarly,the second driver can be selectively operatively coupled to the secondLED configuration as well as the first LED configuration. The associatedcontrol and/or switching circuitry can be configured to monitor anyfault conditions with one of the drivers and effectively switch thesecond driver over to control operation of the first and/or second LEDconfiguration in the case of a malfunction in the first driver. Forexample, FIG. 28 shows an embodiment implementing this concept exceptthat the embodiment of FIG. 28 shows a first LED configuration 20 a anda second LED configuration 20 b, where the first LED configuration andthe second LED configuration are selectively operatively coupled to boththe first driver 52 and the second driver 54. In this embodiment, thecontroller 56 provides similar functionality as that described abovewith respect to FIG. 33.

It will be appreciated that the provision of multiple driving circuitryalong with appropriate control and fault detection circuitry can serveto prolong the rated life of the light fixture. This is due in part tothe fact that in the case of LED-based light fixtures, the associateddriving or control circuitry is more likely to fail than the LED arrayswithin the light fixture.

While aspects of the disclosed technology have been described inconnection with a light fixture having a substantially flat LED panel,it will be appreciated that other LED-based configurations may beemployed. For example, arrays of LEDs may be employed in connection withother focusing and/or brightness-enhancement optical elements besidesthose described above with respect to the various figures.

In addition, the LED panel can include a plurality of LEDs havingoutputs of various colors and/or color temperatures. For example, thesubstantially flat LED panel can include white LEDs having output of apredetermined color temperature. In accordance with another embodiment,the substantially flat LED panel can include multiple arrays of whiteLEDs having outputs of different color temperatures. These multiplearrays can be selectively energized to provide a “white light” of avariable color temperature. Alternatively, the multiple arrays can beselectively energized to maintain a desired overall lumen output toaddress or otherwise compensate for lumen degradation.

In accordance with another embodiment, the substantially flat LED panelcan include a plurality of colored LEDs (e.g., LEDs having red output,green output and blue output), where the colored LEDs are configured tocooperate to produce white light when energized. In the case of aplurality of colored LEDs, the light fixture can include controlcircuitry that is configured to selectively energize the colored LEDs toprovide light output of variable color temperature. The controlcircuitry also can be configured to control the intensity of the lightemitted by the substantially flat LED panel, thereby providing a dimmingfunction.

As described above, the preferred scheme for driving first and secondconfigurations of LEDs is for these configurations to be activatedalternatively. However, in special circumstances in which it isdesirable to provide additional brightness, both configurations can beactivated at the same time. For example, if an ambient light sensor oflight fixture 10 detects brightness below a desired threshold value,light fixture 10 can activate two (or more, if available) configurationsof LEDs at the same time. Alternatively, a stepping function can beapplied to selectively energize multiple configurations of LEDs.

In accordance with one alternative embodiment, the LED panel can includeone or more strips of LEDs disposed adjacent and least one edge of theframe, where each strip of LEDs is removably coupled to the powercircuitry via a suitable electrical connector. It will be appreciatedthat this configuration allows for the easy replacement of one or morestrips of LEDs within the substantially flat LED panel. For example, inthe case of LED failure or burnout, the strip of LEDs could be easilyreplaced without replacing the entire fixture. In addition, the coloroutput of the light fixture could be altered by swapping out one or moreof the LED strips. For example, a holiday effect could be achieved byremoving a strip of white LEDs and replacing the strip of white LEDswith colored LEDs.

To facilitate replacement of one or more LED strips within the flat LEDpanel, the frame can be provided with one or more sections that can bedetached or otherwise separated from the remainder of the frame. Forexample, a cover section of the frame containing an LED strip mayinclude a hinged connection to the remainder of the frame, and a pulltab. The user would pull open the cover section of the frame in order touncover the LED strip for replacement.

In accordance with one embodiment, the light fixture includes at leastone mounting member configured to mount (e.g., removably or permanentlymount) the frame to a support surface. It will be appreciated that themounting member may take on numerous forms depending on the desiredapplication. For example, the mounting member can be configured to mountthe frame to a substantially vertical support surface, such as a wall.In this case, the mounting member may include suitable clips, bracketsor the like configured to anchor the light fixture to a wall in a home,a wall in a hotel, a wall in a parking garage or the like. In anotherexemplary embodiment, the mounting member can be configured to mount theframe to a substantially horizontal support surface, such as a ceiling,the underside of a cabinet or the like. Examples of other applicationsinclude, but are not limited to, stairwell lighting, emergency lighting(optionally including a battery backup), task lighting for cubicles,under counter lighting (e.g., kitchen work areas and within chinacabinets), home or commercial garage lighting, lighting for retailshelving, aquarium lighting, and the like. As is described more fullybelow, the light fixture can be employed in a retrofit kit to retrofitan existing fluorescent lighting unit.

It will be appreciated that the light fixture can be arranged and/orinstalled together with a plurality of light fixtures where a primarylight fixture is electrically coupled to an external power supply andother light fixtures can be coupled to the external power supply by wayof the primary light fixture (so called “daisy chaining”).

Examples of applications include, but are not limited to, stairwelllighting, emergency lighting (optionally including a battery backup),task lighting for cubicles, under counter lighting (e.g., kitchen workareas and within china cabinets), home or commercial garage lighting,lighting for retail shelving, aquarium lighting, and the like. Theprovision of a substantially flat LED panel fixture having edge lightingallows for thin panels of flexible length and width providing uniformlight output.

Although the invention has been shown and described with respect to acertain embodiment or embodiments, it is obvious that equivalentalterations and modifications will occur to others skilled in the artupon the reading and understanding of this specification and the annexeddrawings. In particular regard to the various functions performed by theabove described elements (components, assemblies, devices, compositions,etc.), the terms (including a reference to a “means”) used to describesuch elements are intended to correspond, unless otherwise indicated, toany element which performs the specified function of the describedelement (i.e., that is functionally equivalent), even though notstructurally equivalent to the disclosed structure which performs thefunction in the herein illustrated exemplary embodiment or embodimentsof the invention. In addition, while a particular feature of theinvention may have been described above with respect to only one or moreof several illustrated embodiments, such feature may be combined withone or more other features of the other embodiments, as may be desiredand advantageous for any given or particular application.

What is claimed is:
 1. A light fixture comprising: a frame having athickness of no more than about 1.0 inches and including a first portionof the frame and a second portion of the frame, wherein the firstportion of the frame defines a first channel between a first edge of anoptically transmissive panel and a first outer edge of the frame; asubstantially flat light emitting diode (LED) panel disposed within theframe, wherein the substantially flat LED panel includes an LED stripand the optically transmissive panel, and the optically transmissivepanel is configured to distribute light received at a light-input edgeof the optically transmissive panel from the LED strip, the LED stripcomprising a plurality of LEDs mounted to the second portion of theframe adjacent the light-input edge of the optically transmissive panel;and a first LED driver supported by the first portion of the frame andhoused entirely within the first channel adjacent the first outer edgeof the frame, wherein the first LED driver is configured to receive anAC input from an external AC power supply and to provide a DC output tothe LED strip.
 2. The light fixture of claim 1, wherein the LED strip ismounted to the second portion of the frame adjacent a second outer edgeof the frame.
 3. The light fixture of claim 2, wherein the secondportion of the frame defines a second channel adjacent the second outeredge of the frame, the second channel being configured to support theLED strip.
 4. The light fixture of claim 2, wherein the LED strip issupported by a wall of a second channel, wherein the wall of the secondchannel is offset from the second outer edge of the frame.
 5. The lightfixture of claim 1, wherein the first LED driver includes a transformer.6. The light fixture of claim 1, wherein the frame and the opticallytransmissive panel are rectangular, wherein the frame includes a thirdportion that defines a third channel between a third edge of anoptically transmissive panel and a third outer edge of the frame, andwherein the third outer edge of the frame is opposite the first outeredge of the frame and the third edge of the optically transmissive panelis opposite the first edge of the optically transmissive panel.
 7. Thelight fixture of claim 6, further comprising a second LED driversupported by the third portion of the frame and housed entirely withinthe third channel adjacent the third outer edge of the frame, whereinthe second LED driver is configured to receive a second AC input fromthe external AC power supply and to provide a second DC output to asecond LED strip.
 8. The light fixture of claim 7, wherein the LED stripis incorporated into a first side of the rectangular frame, and whereinthe second LED strip is incorporated into a second side of therectangular frame adjacent a second light-input edge of the opticallytransmissive panel.
 9. The light fixture of claim 1, wherein the frameof the light fixture has a thickness of no more than about 0.5 inches.10. The light fixture of claim 1, wherein the first LED driver includesa circuit board.
 11. The light fixture of claim 1, wherein the first LEDdriver has a length and a width, wherein a length-to-width ratio is atleast 10 to
 1. 12. A light fixture comprising: a frame having athickness of no more than about 1.0 inches and including a first portionof the frame and a second portion of the frame, wherein the firstportion of the frame defines a first channel between a first edge of anoptically transmissive panel and a first outer edge of the frame; asubstantially flat light emitting diode (LED) panel disposed within theframe and having a first face that defines a first plane and a secondface that defines a second plane, wherein the substantially flat LEDpanel includes an LED strip and the optically transmissive panel, andthe optically transmissive panel is configured to distribute lightreceived at a light-input edge of the optically transmissive panel fromthe LED strip, the LED strip comprising a plurality of LEDs mounted tothe second portion of the frame adjacent the light-input edge of theoptically transmissive panel; and a first LED driver supported by thefirst portion of the frame and housed within the first channel adjacentthe first outer edge of the frame, wherein a portion of the LED driveris within at least one of the first plane and the second plane, andwherein the first LED driver is configured to receive an AC input froman external AC power supply and to provide a DC output to the LED strip.13. The light fixture of claim 12, wherein the LED strip is mounted tothe second portion of the frame adjacent a second outer edge of theframe.
 14. The light fixture of claim 13, wherein the LED strip issupported by a wall of a second channel, wherein the wall of the secondchannel is offset from the second outer edge of the frame.
 15. The lightfixture of claim 12, wherein the first LED driver includes atransformer.
 16. The light fixture of claim 12, wherein the first LEDdriver includes a circuit board.
 17. The light fixture of claim 12,wherein the first LED driver has a length and a width, wherein alength-to-width ratio is at least 10 to
 1. 18. The light fixture ofclaim 12, wherein the frame and the optically transmissive panel arerectangular, wherein the frame includes a third portion that defines athird channel between a third edge of an optically transmissive paneland a third outer edge of the frame, further comprising a second LEDdriver supported by the third portion of the frame and housed within thethird channel adjacent the third outer edge of the frame, wherein aportion of the second LED driver is within the plane defined by thelength and the width of the substantially LED panel, and wherein thesecond LED driver is configured to receive a second AC input from theexternal AC power supply and to provide a second DC output to a secondLED strip.
 19. A light fixture comprising: a frame having a thickness ofno more than about 1.0 inches and including a portion of the frame thatdefines a channel between a first edge of an optically transmissivepanel and an outer edge of the frame; a substantially flat lightemitting diode (LED) panel disposed within the frame, wherein thesubstantially flat LED panel includes an LED strip and the opticallytransmissive panel, wherein the optically transmissive panel isconfigured to distribute light received at a light-input edge of theoptically transmissive panel from the LED strip, and wherein the LEDstrip comprises a plurality of LEDs arrayed in a row supported by an LEDbar adjacent the light-input edge of the optically transmissive panel;and an LED driver supported by the portion of the frame and housedentirely within the channel adjacent the outer edge of the frame,wherein a portion of the LED driver is within a plane that is normal tothe LED bar and that contains the plurality of LEDs arrayed in the row,and wherein the LED driver is configured to receive an AC input from anexternal AC power supply and to provide a DC output to the LED strip.20. The light fixture of claim 19, wherein the LED driver has a lengthand a width, wherein a length-to-width ratio is at least 10 to 1.